Summary.
The structure and the gasochromic properties of sol-gel-derived WO3 films with a monoclinic structure (m-WO3) were studied by focusing attention on the size of the monoclinic grains. The size of the m-WO3 grains is modified by the addition of an organic–inorganic hybrid to the initial peroxopolytungstic acid (W-PTA) sols which are based on chemically bonded poly-(propylene glycol) to triethoxysilane end-capping groups (ICS-PPG). The results obtained with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the heat treatment (500°C) of WO3/ICS-PPG (0.5, 1, 2, 5, and 10 mol%) composite films results in a change of their morphology, and nanodimensional pores are formed between the grains. High-resolution TEM (HRTEM) analysis revealed the presence of an amorphous phase on the outside of the m-WO3 grains, whereas energy-dispersive X-ray spectra (EDXS) showed that this amorphous phase contained W and Si. Impregnation of the WO3/ICS-PPG film with H2PtCl6/i-propanol solution followed by heat treatment at 380°C gave the films their gasochromic properties.
Infrared and Raman spectroscopic studies of the WO3/ICS-PPG film confirmed the results of the corresponding HRTEM and EDXS analysis. In situ UV/Vis and in situ IR spectra of the films were measured in hydrogen and in air, and colouring/bleaching changes and the corresponding kinetics were assessed. The IR spectra of gasochromically coloured films showed that the mesoporous WO3/ICS-PPG (1 mol%) film transforms to tetragonal H x WO3 bronze. The IR spectra of the H x WO3 bronze are discussed with the aim to establish the existence of the metal-OH vibrations of gasochromically formed oxyhydroxide tungsten bronze.
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Received October 4, 2001. Accepted (revised) November 19, 2001
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Opara-Krašovec, U., Ješe, R., Orel, B. et al. Structural, Vibrational, and Gasochromic Properties of Porous WO3 Films Templated with a Sol-Gel Organic–Inorganic Hybrid. Monatshefte fuer Chemie 133, 1115–1133 (2002). https://doi.org/10.1007/s007060200082
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DOI: https://doi.org/10.1007/s007060200082